Method and apparatus for routing an underwater cable system

Abstract

A system and method for identifying a route for excavation of an underwater trench on the seafloor includes a surface vessel, a plurality of penetrometers and an onboard computer. As the surface vessel plies along a proposed route for the underwater trench, penetrometers are launched from the vessel at selected launch points. Upon impact of a penetrometer with the seafloor, acoustic signals transmitted from the penetrometer during the impact event are analyzed by the onboard computer. From this computer analysis the seafloor at the impact point is classified as being in either a first state indicative of proceeding along the proposed route or a second state necessitating a deviation from the proposed route. Depending on the state of the seafloor and the number of deviations needed, the proposed route is returned to and followed, or a new proposed route is established. Data from the impact events are subsequently compiled to establish an actual route for excavation of the underwater trench.

We claim: 
     
       1. A method for using a surface vessel to identify a route for excavation of an underwater trench on the seafloor which comprises the steps of: plotting a proposed route for said trench along the seafloor;   locating a launch point;   launching a penetrometer from said surface vessel at said launch point, said penetrometer generating signals during impact of said penetrometer at an impact point on the seafloor;   analyzing said signals for classification of said seafloor at said impact point into a first state or a second state;   proceeding to a location on said proposed route to establish a subsequent launch point when said seafloor at said impact point is in said first state;   establishing a deviation from said proposed route for a subsequent launch point when said sea floor at said impact point is in said second state; and   repeating, as necessary, said steps of launching, analyzing, proceeding and establishing.   
     
     
       2. A method as recited in claim 1 wherein said proceeding step is accomplished by moving said surface vessel through a distance and in a direction from said launch point. 
     
     
       3. A method as recited in claim 1 wherein said step of establishing a deviation further comprises the steps of: assigning a sequence number to said deviation; and   locating said subsequent launch point at a set distance from said proposed route according to said sequence number.   
     
     
       4. A method as recited in claim 3 wherein said set distance is measured along a line from said launch point substantially perpendicular to said proposed route. 
     
     
       5. A method as recited in claim 4 wherein said sequence number is equal to the number of prior said deviations and said set distance is a sequence number multiple of a predetermined distance. 
     
     
       6. A method as recited in claim 1 further comprising the step of corresponding said launch point with said impact point. 
     
     
       7. A method as recited in claim 1 further comprising the step of mapping an actual route for said underwater trench according to impact points analyzed as having a first state. 
     
     
       8. A method as recited in claim 1 wherein said first state corresponds to seafloor characteristics which are conducive to excavation of said underwater trench and said second state corresponds to seafloor characteristics which are not conducive to excavation of said underwater trench. 
     
     
       9. A method as recited in claim 1 wherein an initial launch point is located on said proposed route. 
     
     
       10. A method as recited in claim 1 wherein said locating step is accomplished using the global positioning satellite system. 
     
     
       11. A method as recited in claim 1 wherein said signals generated by said penetrometer are acoustic signals. 
     
     
       12. A method as recited in claim 1 further comprising the step of replotting said proposed route based on analysis of said second state. 
     
     
       13. A system for identifying a route for excavation of an underwater trench on the seafloor which comprises: a surface vessel;   a plurality of penetrometers launchable from said surface vessel, each of said penetrometers generating acoustic signals during impact of said penetrometer at an impact point on the seafloor;   a computer positioned on said surface vessel, said computer being preprogrammed with a proposed route for said trench along the seafloor, said computer being programmable with a launch point whenever one said penetrometer is launched from said surface vessel and, said computer including means for analyzing said signals for classification of said seafloor at said impact point into a first state indicative of proceeding to a location on said proposed route to establish a subsequent launch point or a second state indicative of establishing a deviation from said proposed route to establish a subsequent launch point.   
     
     
       14. A system as recited in claim 13 wherein said surface vessel is moved through a distance and in a direction from said launch point after launching one said penetrometer and wherein said distance is based on analysis of said first state. 
     
     
       15. A system as recited in claim 14 wherein said deviation is assigned a sequence number and said subsequent launch point is at a set distance from said proposed route according to said sequence number, said sequence number being equal to the number of prior said deviations, and said set distance being a multiple of said sequence number and a predetermined distance and measured along a line from said launch point substantially perpendicular to said proposed route. 
     
     
       16. A system as recited in claim 15 wherein said computer further comprises: means electronically connectable with said computer for inputting said launch point based on data from the global positioning satellite system; and   means for corresponding said launch point with said impact point.   
     
     
       17. A system as recited in claim 16 wherein said computer further comprises means for mapping an actual route for said underwater trench according to impact points analyzed as having said first state. 
     
     
       18. A system as recited in claim 17 wherein said penetrometer is configured to penetrate less than four feet into the seafloor for seafloor characteristics corresponding to said first state.